Month: December 2015

There are many factors to consider before buying an IP surveillance camera – a digital security camera that uses a computer network to send video – for your business. This introduction to digital imaging from TriTech helps you understand the elements that go into a video from an IP camera.

IP camera information sheets of technical specifications and data can be overwhelming to read through. Without knowledge of what different frame rates mean or when the f-number is important, it can be very difficult to know which specifications matter most to get the best surveillance video of your business.

Whether a video or still photo, there are two parts of any image: detail and clarity.

Details

Resolution. Resolution is the number of pixels that the sensor of an IP camera provides an image based on pixel count.

If you need to examine details that are small such as license plates or distant objects, resolution would be one of the more important factors because more pixels of the small details are collected.

Otherwise, just how important is resolution to you?

So many other factors go into the actual image (including those discussed below) that, essentially, resolution can be viewed as a stage where the other factors perform. The abilities of the director, actors, lighting, and sound take priority over the stage. If the other factors can’t do well, it will show on stage.

A common misconception is that resolution is the most important thing. Make sure your IP camera has the ability to capture what you want first.

Resolutions used by IP cameras

How does resolution actually work? Think of it as the sensor’s box.

1600×1200 is a larger dimension than 1280×800 and therefore has a higher pixel count, representing the measurement of the box. 1280×800 cannot collect as many pixels as 1600×1200 because of the difference in available space, representing the area inside the box.

It’s also the reason why small images become fuzzy when enlarged. There aren’t enough pixels collected by a 1280×800 box to fill a 1600×1200 box, so each pixel reaches out to fill the space available.

Frame Rate. Frame rate specifies how often a camera creates frames of a scene.

If the speed of subjects plays a part in what will be filmed, frame rate is especially important; the faster the speed, the higher the frequency that’s needed to keep up. Situations such as accidents, theft, or threats will also be easier to clarify.

Comparison of frame rates in a one-second duration.

If you film at 5 fps (frames per second) with a narrow field of view of a door or hallway, a person running may be recorded once or not even at all. On the other hand, if the scene is steady like a factory or hotel lobby or if field of view increases, a higher frame rate isn’t necessary.

With a higher frame rate, you’ll document a more fluid video and more precise scene but it’ll take up more of your storage. A lower frame rate will use less storage but can cause “strobing” effects that may be unpleasant on your eyes.

Clarity

Exposure. Exposure is how much light reaches the sensor as dictated by the f-number and dynamic range.

If there is less light, then the sensor needs more exposure time to get the right amount of light. Unfortunately, the more time for getting light can also get visible noise (graininess) and smeared movement.

Comparison of Exposures

The exposure outcomes are similar to the “Story of the Three Bears;” overexposed is too bright, underexposed is too dark, and the proper exposure is just right.

F-number (or f-stop) is a lens’ ability to gather light, measured by the ratio of the focal length (distance between the lens and sensor) to the aperture (iris opening) diameter.

The f-number of an IP camera for business is particularly important for indoor use and areas of limited light. If you’re filming a room or lobby and can’t see any of the video because it’s too dark, it won’t do you much good. A lower f-number has a better chance of delivering clear video because the aperture is more open to gather more light for the sensor, shining light onto the pixels and your image.

In contrast, if lighting isn’t an issue for your business needs, f-number also represents depth of field, which is explained below.

Dynamic range is the ratio between the brightest and darkest illuminations of a scene. A limited dynamic range is a very small window that will leave the contents of dark areas concealed or magnify the brightest spot.

Outdoor surveillance, building entrances, or cameras including windows will be visually enhanced with a wide dynamic range (WDR). If you’re filming and can’t see any of the video because the light washes everything out, it won’t do much good. WDR controls the effect of bright light while revealing shadows and dim spots.

Wide Dynamic Range, without and with.

Provided by many IP cameras, WDR is a very extensive scale that can process both dark and light into one frame. The sensor does this by taking different exposures, pulling light from the underexposed and dark from the overexposed, blending the patches near these areas, and making one polished image.

Depth of Field. Depth of field is the distance around the point of focus that’s equally as sharp. A larger f-number gives a larger area of focus.

Depth of field is important if objects over a long range need to be in focus, such as identifying a row of license plates or searching faces of a large area.
Field of view is how much of the field (scene) you can view, while depth of field is how much of the field is in focus.

For example, teller windows inside a bank with an IP camera focused on the front of a customer’s face. The depth of field would be the clarity, if any, in front of (the bank teller, teller’s computer, counter, register) and behind (line of customers, lobby, main entrance) them.

TriTech is the only choice for your business

Since 1993, TriTech has been unmatched in expertise and service. Our quality partners, including Axis and Mobotix, independently certify our technicians and engineers for consistent success. TriTech serves businesses of all sizes and designs custom IP surveillance solutions.

If you want to understand more about the digital imaging of video or how an IP camera can help your business, call TriTech today at (262) 717-0037 or toll-free 24/7 at (800) 891-3388.